1. Field of the Invention
This invention relates to a method for fabricating semiconductor devices and a semiconductor device made therefrom, more particularly to a method for fabricating semiconductor devices involving removing a temporary substrate without cutting a semiconductor structure formed thereon.
2. Description of the Related Art
Currently, there are various optoelectronic semiconductor devices on the market. Taking an example of a vertical-conducting light-emitting diode (LED), referring to FIG. 1, such optoelectronic semiconductor device 1 comprises a conductive member 11, an epitaxial structure 12 disposed on the conductive member 11, and an electrode 13 disposed on the epitaxial structure 12. By virtue of electrical connection with the conductive member 11 and the electrode 13, electricity may be supplied to the epitaxial structure 12 so that light may be emitted through an optoelectronic effect.
When fabricating the optoelectronic semiconductor device 1 (the vertical-conducting LED), a sapphire (Al2O3) substrate, which has a better lattice match for an epitaxial film layer formed thereon and is in a form of a wafer, is selected to serve as a temporary substrate. Then, on the temporary substrate, the epitaxial film layer of gallium nitride (GaN) is epitaxially grown; a conductive layer serving as a permanent substrate (which forms a plurality of the conductive members 11 after cutting) is formed on the epitaxial film layer; and the temporary substrate is subsequently removed from the epitaxial film layer. Thereafter, a plurality of the electrodes 13 are formed on a surface of the epitaxial film layer that is exposed after the temporary substrate is removed, followed by cutting into a plurality of the optoelectronic semiconductor devices 1.
In the above conventional process, the temporary substrate is removed from the epitaxial film layer using a laser lift-off process or a mechanical polishing process. However, the laser lift-off process involves a relatively high fabrication cost, whereas the mechanical thinning process involves the step of directly grinding and polishing off the temporary substrate. The mechanical thinning process is likely to induce a residual stress that could damage the structure of the epitaxial layer stack.